Inverter choice

[sharpener]

Not voltage but frequency. When offgrid the Victron has freedom to increase the frequency and this is used to shut down the PV inverter. They specify max PV no greater than charger rating so there is always somewhere for it to go while this happens (?a few cycles).

More modern inverters have proportional output control based on freq but mine just shut off for 5 mins and the system runs off the batts meanwhile. The frequency drifts back slowly down to 50Hz allowing it to re-synchronise over a further 5 mins. Rinse and repeat. I was surprised how well this works with 11 y.o. StecaGrids but it seems it has been in the international specs for a lot longer than that.

[nowty]

My SMA system does frequency shift throttling so all the PV inverters still operate offgrid even with full batteries.

[openspaceman]

So the multiplus increases the frequency enough to shut down the FIT inverter, in my case a Solarmax, but not too much to upset any other equipment. The FIT inverter then shuts down until there is a call from the multiplus for more power by reducing the frequency? Saves having a contactor to shut down the panels.

[Fueltheburn]

This is exactly what I want to avoid.
I will leave the FIT untouched on the AC input line of the multiplus.
The FIT inverter should shut down under grid fail conditions and the Multiplus should also block off sending anything to the grid also under the same conditions.

My hope is that the secondary panels connected directly to the multiplus will still remain active during the grid shutdown period.

[sharpener]

This is exactly what I want to avoid.

The FIT inverter should shut down under grid fail conditions and the Multiplus should also block off sending anything to the grid also under the same conditions.

Why, what is wrong with allowing it to meet the house loads if it wants to? The Multiplus will shut down the MPPT first before the FITs if there is too much PV which is to your advantage. You can see this in the screenshot below when the immersion heater cuts out at 1346 and the E roof MPPT (which has been tracking the W roof) suddenly drops in power.

[Fueltheburn]

My concern was as you stated. I was concerned the FIT may shutdown or throttle back if demand was being met by the mppt connected string to the multiplus.
This is an old tariff so is still quite financially beneficial.

[Fueltheburn]

Would you put the FIT inverter on the grid connected load output or the 50A UPS load on the multiplus?

I am going through the manual today and am assuming I will come across this in a schematic shortly.

[sharpener]

My concern was as you stated. I was concerned the FIT may shutdown or throttle back if demand was being met by the mppt connected string to the multiplus.
This is an old tariff so is still quite financially beneficial.

No, it tries to downregulate the MPPT first, so preserving your FIT income as long as possible.

Would you put the FIT inverter on the grid connected load output or the 50A UPS load on the multiplus?

I am going through the manual today and am assuming I will come across this in a schematic shortly.

See also the Victron "Wiring Unlimited" manual online. Presumably you have found the Victron discussion site?

Not quite sure I understand the distinction you are making.

I have my entire house CU and the FIT inverter both connected to AC-Out 1. There are no loads on the input side or AC-Out 2. The planned HP though will go on the grid side, I have just fitted a mini-CU for the purpose.

There is a bypass for the house, and a separate one for the garage so I can charge the EV overnight on E7 without any risk of running down the house battery.

[openspaceman]

No, it tries to downregulate the MPPT first, so preserving your FIT income as long as possible.

Is this only when islanded i.e. off grid or even when on grid?

[sharpener]

No, it tries to downregulate the MPPT first, so preserving your FIT income as long as possible.

Is this only when islanded i.e. off grid or even when on grid?

Either. The pix upthread are on-grid but the behaviour is the same offgrid.

Ongrid you can also select separately whether the DC and AC generation export or not. I sometimes turn off the DC export because inverting it to AC results in a lot of fan noise, also I don't like to use the MPPT if there is no financial benefit as it runs quite hot. [Posted this last night but it seems to have disappeared]